The importance of carbon sequestration in soils

I discussed carbon farming in a series of earlier posts; I have given links to some at the end. There I was trying to understand soil sequestration of carbon in particular.

I was interested for several reasons. Proponents argued that improved farming techniques would both reduce CO2 in the atmosphere and improve soils, a win-win situation. Further, the numbers quoted were very large.

I was also interested because the waves of bush protests that would finally help bring down both a prime minister and an opposition leader had already begun, if still below the radar of the city media. To they degree they were being picked up, they were still being treated as an aberration, a somewhat strange side show.

Central to those protests were farmer concerns about increasing land use controls usually justified on environmental grounds. Farmers were also alarmed at the way that farming land was or might be locked up in forests in the name of action to reduce CO2. These concerns and alarms fed into increased opposition to the very concept of climate change itself. Carbon sequestration in soils became a major issue because it offered an apparent win-win way out that did not require removal of farm land from production.

Before going on, I should make my position on climate change clear for the benefit of those reading this post in isolation from my previous writing. I believe on the balance of probabilities that human induced climate change is real and needs to be addressed. Accepting this, I have had a two-fold concern: I wanted to understand as best I could the various alternative solutions proposed and also wished to identify likely adverse and especially unforeseen results. Quite a bit of my writing on this blog has been concerned with perverse outcomes from public policy.

One outcome of the debate was Labor's $45 million Carbon Farming scheme.

In today's on-line Sydney Morning Herald Tom Arup's Farm scheme will reap only minimal carbon cuts, says department reports on a Department of Climate Change and Energy Efficiency Report. Tom's story says in part: 

The estimates show that even under the most optimistic scenario, storing more carbon in cropping land will save less than 1 million tonnes of carbon a year by 2020. Savings from soil carbon cannot be counted towards Australia's emissions reduction targets under international rules.

The estimates instead show most savings under the scheme will be driven by reducing deforestation and better management of waste.

This conclusion is at such variance with carbon farming advocate Dr Christine Jones (a former CSIRO scientist) estimate that Australia could sequester 685 million tonnes of carbon by increasing soil carbon by half a per cent on only 2% of the farms that it pulled me up short.

Those who are interested will find the Department's report here. The first thing that I noted in the report was the distinction between Kyoto compliant and non-compliant activities. This is actually something that has been worrying me because of the way it drives policy in directions that are not necessarily sensible at local level.

In terms of soil sequestration itself, the Department says:    

Increased soil carbon on cropping land

Assuming gradual uptake, it is estimated that increased soil carbon, or reduced losses, on cropping land could deliver abatement of between 0.3 and 0.5 Mt CO2-e per year by 2020.

Key assumptions:

• The CSIRO national potential for building soil carbon, which also includes the mitigation of N2O emissions for cropped land, is estimated to be 25 Mt CO2-e per year.
• We assume that Australia's technical potential is 10 per cent of the CSIRO4 national potential, given the assumptions made by CSIRO about the relationships between potential and attainable estimates of soil carbon sequestration and nitrous oxide reduction for Queensland soils. On this basis, Australia‟s technical abatement would be 2.5 Mt CO2-e per year by 2020.
• In the high scenario, uptake by 2020 is assumed to be 20 per cent of the technical potential, leading to abatement of 0.5 Mt CO2-e. In the low scenario uptake by 2020 is assumed to be 10 per cent of the technical potential, leading to abatement of 0.25 Mt CO2-e.
• The implementation of conservation farm management practices is continued over time to ensure the maintenance of the rate of sequestration and, once the new higher soil carbon stock equilibrium is reached, to ensure permanence of that higher soil carbon stock.

Background:

• Most current practices for sampling and analysis may be relatively expensive, but new and emerging techniques may reduce this cost over time.
• The technical potential for the soil carbon sequestration rate is likely to be less than the value given in the CSIRO report4 because this value is a combination of both soil carbon sequestration and reduction in soil nitrous oxide emissions.
• The CSIRO estimated a national potential for building soil carbon and mitigation of N2O emissions for cropped land of 25 Mt CO2-e per year.
• The potential soil carbon sequestration rate assumes that the sequestered carbon will remain permanently in the soil. A change in farming practice, for example from pasture to cropping or no-tillage to tillage may lead to a loss of the sequestered carbon. In the CSIRO Report this reduces the overall abatement potential. Adherence to CFI methodologies would minimise the risk of losing sequestered soil carbon and allow abatement to continue to occur for as long as sequestration continues to raise stocks of carbon in the soil.
• In other CSIRO work (Sanderman et al., 2010) the annual per hectare rates of sequestration were identified as being highly variable, with a range from 0 to 0.6 tC/ha/yr depending upon climate, soil management and vegetation.4 The land area associated with any soil carbon sequestration rate will define the national potential. Care must be taken in the appropriate allocation of land use and assessment of climate when estimating sequestration rates.

4. Sanderman, J., R. Farquharson and J. Baldock , Soil Carbon Sequestration Potential: A review for Australian Agriculture (July 2010).

I don't know what this actually means. I couldn't find the journal article in question in the available time, but I did find this 2010 paper by Jonathan Sanderman and Jeffrey A Baldock Accounting for soil carbon sequestration in national inventories: a soil scientist's perspective. It concludes: 

Results from agronomic field trials generally show a relative gain in carbon stocks with implementation of management practices that return or retain more of the carbon captured by growing plants. However, much of the data used to support such a conclusion has been derived from point-in-time measurements which are ambiguous as to whether the relative difference was due to net sequestration or simply a cessation of losses during the trial (i.e. an avoidance of emissions).

While all of the scenarios in figure 1 represent a real net benefit to GHG abatement, we have argued here that (1) the predictive power of results from most agronomic field trials to alternative situations where these management practices have been implemented is questionable without detailed knowledge of the state of the soil carbon system; and (2) the current recommended IPCC accounting methodologies may not properly credit these activities and may indeed result in contradictory results when accounted for using tier I or II versus tier III approaches. Given that GHG credits for soil carbon sequestration will not be widely included during the first commitment period (2008–2012) of the Kyoto Protocol, there is time to develop more robust accounting systems that correctly credit agricultural management activities.

Now if you look at this piece by some of the same authors you can see that there are savings, but we have measurement and accounting problems. Another 2010 paper that I found by Craig Liddicoat, Amanda Schapel, David Davenport and Elliot Dwyer focused on South Australia says in part:

According to CSIRO estimates, Australia’s current Kyoto Protocol commitments (which don’t include soil carbon) already open the door to nearly 80% of the carbon sequestration potential of the continent, mainly In the form of forestry. CSIRO also estimates soil carbon to offer around 2.5% of the national sequestration potential, and this would be unevenly distributed towards favourable climates and soil types. Given our predominantly low rainfall and sandy soils, South Australia is not expected to be a large player in the area of soil carbon sequestration or trading. However, this view does not take into account the potential offered
through soil modification. This highlights that an audit of existing capacity, and potential to improve capacity in South Australian soils is a key piece of work needed to build our understanding and support involvement of landholders in any carbon trading scheme.

Now what does all this tell us? It seems to me just this:

1. At farm level, we have a group of enthusiasts including scientists who believe that carbon sequestration in soils is very important and who have been campaigning for a number of years to change farm practices and to get scientific recognition. As I have discussed before, this is actually the way in which much agricultural innovation has occurred in Australia.
2. At the official scientific level, we have acceptance that carbon sequestration in soils occurs, but no one is quite sure by how much nor how to measure it. The combination of enthusiasts with politics seems now to be driving increased research.
3. At official or public policy level internationally and until recently locally, carbon sequestration in soils has been excluded from consideration as not important, immeasurable or irrelevant because its effects cannot be measured and therefore cannot be included in things such as carbon pricing or emission trading schemes.
4. At political level, carbon sequestration in soils has become another card to play in the shifting debate.          

I now want to finish this post by making an extreme claim, that the question of carbon sequestration in soils and especially agricultural land may well be the most important climate change issue facing Australia today. I say this for the following reasons:

1. Carbon sequestration in soils appears to be the one really genuine win-win possibility in the climate change debate. Environmentalists would argue that the growth of sustainable jobs will more than offset other job loses, so we still win. Let's accept this for the purposes of argument. However, those who lose their jobs will, on experience, not be the same as those who get the new jobs. That's not really win-win.
2. At a time when global food prices are skyrocketing and food security has been identified as a key global issue, it doesn't make a lot of sense to take land out of agricultural production unless there is no other choice.
3. The upper limit numbers attached to carbon sequestration in soil remain huge. Accepting that there are problems in the numbers, it would still seem sensible to devote resources to exploring possibilities.

Selected Past Posts

• 13 September 2009 Sunday Essay - Farming, green house gases and the importance of practical experiments- Part One
• 20 September 2009 Sunday Essay - Farming, green house gases and the importance of practical experiments- Part Two
• 26 November 2009 Australian responses to climate change - a background briefing
• 15 April 2010 Belshaw's position on climate change. This post contains links to range of previous posts on the issues 
• 9 March 2011 Agriculture, innovation & the individual

Postcript

One of the difficulties in the issues I have been discussing is the growing divide between urban and country Australia. In this context I was struck by this article: Give animals property rights: uni lecturer. I won't comment further.

Postscript Two

In a comment, KVD wrote:    

Hi Jim

Cut/pastes from your essay:

CSIRO:
Most current practices for sampling and analysis may be00 relatively expensive, but new and emerging techniques may reduce this cost over time.

Sanderman & Baldoch:
there is time to develop more robust accounting systems that correctly credit agricultural management activities

Liddicoat, Schapel, Davenport, Dwyer:This highlights that an audit of existing capacity, and potential to improve capacity in South Australian soils is a key piece of work needed

Now perhaps it’s just me, but there seems to be a pattern in the above comments.

And then there’s your “it would still seem sensible to devote resources to exploring possibilities” – with which I absolutely agree. But I’m assuming you are talking about improved sequestration techniques, not the accounting therefore?
kvd

I thought it worthwhile bringing KVD's comment up into the main post because it does illustrate an important issue that I have discussed, the way that the need to measure things for accounting and management purposes (you can't have a trading or at least a performance measurement scheme without this) affects research.

To my mind, research into improved sequestration techniques is key, accounting and measurement techniques secondary. Obviously you have to be able to measure the results of research, that's part of the process, but that's a different if related issue from aggregate assessments.